Thermally exfoliated graphite oxide (TEGO) (also known as functionalized graphene sheets) has been disclosed in US patent application publication US 2007/0092432; Schniepp, H. C. et al. J. Phys. Chem. B. 2006, 110, 8535-8539; McAllister, M. J. et al. Chem. Materials 2007 19, 4396-4404; and Kudin, N. K. et al. Nano Letters 2008, 8, 36-41, which are hereby incorporated by reference herein. Graphite oxide is formed by the treatment of graphite with oxidizing agents and intercalants or other oxidizing means and has a high oxygen content. During the thermal exfoliation of graphite oxide, oxygen functionalized sites on the graphite oxide decompose to evolve oxygen-containing gases that are liberated from the system, resulting in a thermally exfoliated graphite oxide that typically has a lower oxygen content on a molar basis than does the starting graphite oxide. The forgoing references disclose the formation of graphite oxide having carbon to oxygen molar ratios of between about 1.5:1 and 20:1.
However, in many applications, it would be desirable to obtain functionalized graphene sheets (FGS) having a higher carbon to oxygen ratio. For example, the amount of oxygen functional groups can affect the reactivity of the FGS with a polymer matrix when they are used as reinforcement fillers and/or affect nature of an adsorbed layer at the FGS interface; the presence of oxygen can be deleterious in certain applications; and the presence of oxygen-containing functional groups on the FGS can disrupt the pi-conjugated system, which can decrease the electrical conductivity of the material.